The invention is directed to a semiconductor light-emitting diode such as is known generically from U.S. Pat. No. 5,216,263 A.
For several decades, LEDs and LED array chips have been used for displaying graphic characters. For this purpose, for example, 7-segment LED display chips were developed by means of zinc diffusion or zinc implantation in a thick, n-conducting GaAsP (gallium arsenide phosphide) layer on a GaAs (gallium arsenide) substrate and are still produced today based on the same technology. In this case, typical light intensities reach 0.1 mcd/segment when operated at 5 mA current strength. The emission wavelength is limited by the material to 650-660 nm (red light) at which the sensitivity of the human eye is only about 10%.
Other LED display components have been developed as hybrid elements in which more efficient LED chips (approximately 10% efficiency) with different emission wavelengths in the visible spectrum were combined and arranged. However, the size of these elements prohibits their use in very compact spaces, e.g., in the beam path of optical equipment.
Translucent LCD displays with LED backlighting are also used for displaying graphic characters. They are usually relatively large displays so that the LED backlighting is carried out exclusively by arrays of discrete LEDs or LED chips on a supporting board. The LEDs of an array can be controlled collectively as well as individually. The LED backlighting may be monochromatic, multicolored or white.
To allow for more compact sizes, the semiconductor layers (epitaxial structures) must be structured on a small scale and their optical and electrical characteristics adapted. In addition to diffusion, so-called implantation of protons or other electric charge carriers through irradiation can alter or even destroy the crystal structure so that the irradiated (implanted) areas lose their electric conductivity partially or completely. Further, these areas can be absorbent for certain wavelengths. The alteration of the crystals can be controlled through the choice of the kinetic energies imparting the electric charge carriers and through the quantity of electric charge carriers per unit area (dose) of a beam bundle used for the irradiation. In order to generate so-called deep implanted regions, the electric charge carriers are radiated onto the material with high energy but at a low dose, whereas low energies and high doses are used for generating surface implanted regions.